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What Factors does Cost Saving Mode Take into Consideration?

RKCRLR

Member
Apr 13, 2020
285
106
Garden Valley, CA
Obviously, Cost Saving mode takes the different TOU rate periods into consideration.
But does it take NBCs into consideration?
How about battery cycle life?
Or the round efficiency loss?
I'm assuming it only takes the rate periods into consideration but was wondering if anyone knows for sure.
 

wjgjr

Active Member
May 11, 2020
1,078
809
Silver Spring, MD
Tesla knows nothing about your rate structure other than your self-identified peak, shoulder, and off-peak times, so it cannot take into account NBCs, nor does it know whether the round-trip lost makes shifting uneconomical.

It is possible that it takes battery life into account, though I don't think there is much official from Tesla in terms of what they do or recommend as far as battery life.
 

RKCRLR

Member
Apr 13, 2020
285
106
Garden Valley, CA
What would be nice is if Tesla added fields for NBCs and actual rate costs in the app. That way it could make better cost saving decisions.
For me, I'd like a mode that targets a $0 True-Up and maximizes reserve in the winter.
 

h2ofun

Active Member
Aug 11, 2020
1,613
262
auburn, ca
What would be nice is if Tesla added fields for NBCs and actual rate costs in the app. That way it could make better cost saving decisions.
For me, I'd like a mode that targets a $0 True-Up and maximizes reserve in the winter.
I have just left mine on balanced, peak 3 to 12pm. runs mostly off batteries and solar. I do not need anymore options for me. And yep, I expect a generation credit. :)

p.JPG


b.JPG
 

RKCRLR

Member
Apr 13, 2020
285
106
Garden Valley, CA
I switched mine from Cost Saving to Balanced since it appears I'm on track to get a credit.
But this winter isn't typical (hopefully). Additionally, my wife has been working from home due to COVID so that throws another wrench into the data for next year's planning.
 

holeydonut

Supporting Member
Jun 27, 2020
1,026
604
East Bay NorCal
Yeah, managing the winter months seems to be something that requires grid-charging during the low-cost off-peak time instead of something that can be managed on a day-to-day basis with the app :(
 
Mar 15, 2021
63
30
California
I've switched back and forth between Cost Savings and Balanced and didn't notice any net difference in grid consumption vs sending it back to the grid on sunny days this time of year

A typical full sunny day on Balanced:
1 to 3 kWh from grid
12 to 16 kWh to grid
= net 11 to 15 kWh to grid

A typical full sunny day on Cost Savings:
5 to 8 kWh from grid
18 to 20 kWh to grid
= net 10 to 15 kWh to grid

On the days where I use more from the grid I also send less to the grid.

Now during overcast or rainy days, costs savings is the only way I can fully charge my battery between the two settings most of the time. During winter cost savings does send slightly more net back to the grid.
 

RKCRLR

Member
Apr 13, 2020
285
106
Garden Valley, CA
Yeah, managing the winter months seems to be something that requires grid-charging during the low-cost off-peak time instead of something that can be managed on a day-to-day basis with the app :(
It depends on the size of the system. If one's system is large enough, the winter battery reserve could be set very high in the winter for possible power outages and then low in the summer to make up for the peak rates paid in the winter.
As long as I get to a $0 True-Up all is good. I'd just like the system to figure it out for me.
 
Mar 15, 2021
63
30
California
I've switched back and forth between Cost Savings and Balanced and didn't notice any net difference in grid consumption vs sending it back to the grid on sunny days this time of year

A typical full sunny day on Balanced:
1 to 3 kWh from grid
12 to 16 kWh to grid
= net 11 to 15 kWh to grid

A typical full sunny day on Cost Savings:
5 to 8 kWh from grid
18 to 20 kWh to grid
= net 10 to 15 kWh to grid

On the days where I use more from the grid I also send less to the grid.

Now during overcast or rainy days, costs savings is the only way I can fully charge my battery between the two settings most of the time. During winter cost savings does send slightly more net back to the grid.
Here was our last full sunny day 3 days ago. I was on balanced.
 

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Mar 15, 2021
63
30
California
I've switched back and forth between Cost Savings and Balanced and didn't notice any net difference in grid consumption vs sending it back to the grid on sunny days this time of year

A typical full sunny day on Balanced:
1 to 3 kWh from grid
12 to 16 kWh to grid
= net 11 to 15 kWh to grid

A typical full sunny day on Cost Savings:
5 to 8 kWh from grid
18 to 20 kWh to grid
= net 10 to 15 kWh to grid

On the days where I use more from the grid I also send less to the grid.

Now during overcast or rainy days, costs savings is the only way I can fully charge my battery between the two settings most of the time. During winter cost savings does send slightly more net back to the grid.
And here was the last sunny day on cost savings.
 

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RKCRLR

Member
Apr 13, 2020
285
106
Garden Valley, CA
I've switched back and forth between Cost Savings and Balanced and didn't notice any net difference in grid consumption vs sending it back to the grid on sunny days this time of year

A typical full sunny day on Balanced:
1 to 3 kWh from grid
12 to 16 kWh to grid
= net 11 to 15 kWh to grid

A typical full sunny day on Cost Savings:
5 to 8 kWh from grid
18 to 20 kWh to grid
= net 10 to 15 kWh to grid

On the days where I use more from the grid I also send less to the grid.

Now during overcast or rainy days, costs savings is the only way I can fully charge my battery between the two settings most of the time. During winter cost savings does send slightly more net back to the grid.
My understanding of Balanced is one of the things it will do is allow the home to use solar power instead of grid power when the Powerwalls need to be recharged during off peak. Cost Saving will prioritize Powerwall recharging instead of solar home use during off peak. Once the Powrwalls are recharged, it will switch to allowing the home to use solar power during off peak instead of sending it to the grid.
Allowing the home to use solar during off peak should reduce NBCs.
 
Mar 15, 2021
63
30
California
My understanding of Balanced is one of the things it will do is allow the home to use solar power instead of grid power when the Powerwalls need to be recharged during off peak. Cost Saving will prioritize Powerwall recharging instead of solar home use during off peak. Once the Powrwalls are recharged, it will switch to allowing the home to use solar power during off peak instead of sending it to the grid.
Yes. In balanced when my batteries are low solar will first supply the house and net solar production above what the house uses is then sent to batteries. In cost savings all the solar first goes to the batteries and the house gets energy from the grid. Only once the batteries are full does solar then go to the house.

Similar with discharging during shoulder. In balanced solar will still supply the house during shoulder with excess still going to the grid. And then when solar production becomes too low to supply the house the battery will supplement. Whereas in cost savings during shoulder the battery will solely supply the house and all solar will exclusively go to the grid

Both behave the same during peak. All solar goes to grid and house runs off battery.
 

h2ofun

Active Member
Aug 11, 2020
1,613
262
auburn, ca
My understanding of Balanced is one of the things it will do is allow the home to use solar power instead of grid power when the Powerwalls need to be recharged during off peak. Cost Saving will prioritize Powerwall recharging instead of solar home use during off peak. Once the Powrwalls are recharged, it will switch to allowing the home to use solar power during off peak instead of sending it to the grid.
Allowing the home to use solar during off peak should reduce NBCs.
I am on off peak now. My home is being run from the solar. Excess is all going to batteries. Nothing to and from grid which is what I want, to be totally off the grid.
 

getakey

Active Member
Jan 28, 2020
1,048
331
95762
It depends on the size of the system. If one's system is large enough, the winter battery reserve could be set very high in the winter for possible power outages and then low in the summer to make up for the peak rates paid in the winter.
As long as I get to a $0 True-Up all is good. I'd just like the system to figure it out for me.

Thats what I do. In the winter I have my reserve at 75 to 80%. In summer I drop it to 33%. I have 3 PWs and use Cost Savings. I added PWs to existing solar. I was pretty close to $0 true-p before the PWs. I think it was ~$150. With PWs, I know I'll be negative, but I will be moved off my current rate plan in a couple years. At that point, I expect to get back to around $0
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
7,734
8,547
Riverside Co. CA
Obviously, Cost Saving mode takes the different TOU rate periods into consideration.
But does it take NBCs into consideration?
How about battery cycle life?
Or the round efficiency loss?
I'm assuming it only takes the rate periods into consideration but was wondering if anyone knows for sure.

I think there is virtually zero chance that tesla, now or in the future programs anything into the system regarding "battery cycle life". Teslas whole mantra is "just use it", "just plug it in". The minute they (for example) give options to only charge to 90%, or mention anything about minimizing battery cycles, they get flooded with people wanting more data about this or that charging cycle etc.

The number of "battery" threads in the car sections is staggering, for example.

Teslas answer to "minimize cycle life" is "We provide a 10 year warranty that the battery will maintain at least 70% capacity, when charged by solar power, unlimited cycles".

If they programmed anything into the system regarding round trip cycle losses, that would bring that front and center for people who currently dont know or care about that, so I would bet you never see anything officially from tesla programing around round trip efficiency loss either. This is basically emphasizing that people are losing a portion of their electricity by running it through their expensive batteries they purchased.

There is no upside to them doing that, only downside, from a business perspective.
 
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astrorob

stealth performance M3
Aug 27, 2014
397
73
oakland, ca
per my recent thread, once my solar production got above a certain level, the cost saving mode seems to have started realizing that it doesn't need to charge the powerwall to 100% every morning, as i've been finishing the peak time with power to spare above the reserve threshold. before that point it was charging to 100% every day (or as high as it could get before peak started.) so there was a big change in the behavior as winter ended.

also per that thread and the helpful replies, it looks like as the week progresses toward the weekend the software realizes that it can charge more cheaply on the weekend and reduces the peak charge even more on thursday/friday.

and just now i noticed it backing off on the charge rate between 90 and 95% which i don't think i've seen before.

so it really does take a lot of factors into consideration, but as far as i can tell these are focused on round-trip efficiency losses.
 

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Nov 28, 2018
7,734
8,547
Riverside Co. CA
per my recent thread, once my solar production got above a certain level, the cost saving mode seems to have started realizing that it doesn't need to charge the powerwall to 100% every morning, as i've been finishing the peak time with power to spare above the reserve threshold. before that point it was charging to 100% every day (or as high as it could get before peak started.) so there was a big change in the behavior as winter ended.

also per that thread and the helpful replies, it looks like as the week progresses toward the weekend the software realizes that it can charge more cheaply on the weekend and reduces the peak charge even more on thursday/friday.

and just now i noticed it backing off on the charge rate between 90 and 95% which i don't think i've seen before.

so it really does take a lot of factors into consideration, but as far as i can tell these are focused on round-trip efficiency losses.

I never considered that cost savings mode might actually take round trip losses into effect. My thought was more along the lines that it figured "I dont need full battery to make it through the defined peak period, XX is enough, so let me export solar for credit".

Its somewhat semantics though, since exporting the solar avoids round trip.
 

MorrisonHiker

S 100D 2021.4.15
Mar 8, 2015
9,436
8,582
Colorado
If you want to be completely off grid or as much as possible, then Self Powered mode would be best
The problem with that is there's no "scheduled Self-powered" mode and you might run out of battery before or during peak and then pull from the grid and pay peak rates.

In order to power my house off-grid as much as possible, I use Balanced but set the shoulder period to be much longer, such as 7 pm until 3 am. I then have off-peak start at 3 am instead of 7 pm and only last for a couple hours. This way, I really only use grid power for a few hours a day and the peak period is always covered by Powerwalls.
 

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